In present-day communications, optical methods for transmitting and processing information are attractive and promising, since they offer extraordinary advantages over all other types of communication methods. It is necessary to view and register optical images using the eye, video cameras and other light-sensitive devices in order to record optical information provided by light sources of different intensities (e.g., lasers, the sun, lamps, etc.)
Photosensitive media must be protected against being blinded and possibly damaged by incident light of excessive intensity. Safety devices normally used for this purpose have numerous disadvantages: neutral or polarizing filters also diminish the brightness of the objects to be observed, together with that of the interfering light. If the lighting is diminished, these filters are mechanically removed. Known eyeglasses, switched automatically to absorbing filters by strong incident light, reduce the overall visual field. A better protection is offered by locally reducing the brightness of strongly illuminated objects situated in the visual field of the eye, video camera, etc., without suppressing poorly illuminated objects at the same time.
One solution is provided by Optically Addressed Spatial Light Modulators (OASLM). Safety glasses using optically addressed spatial light modulators (OASLM) are described by M.G. Tomilin, A.P. Onokhov, and D. Yu. Polushkin in Mol. Cryst., Liq. Crys., 222, 119, (1992). In this case, the twisting effect in nematic liquid crystals is used as the medium affecting the light. The basic disadvantage of the use of nematic liquid crystals is their relatively slow switching time (approx. 10.sup.-2 s). This results in blurring of the suppressed image during the motion of bright objects in optically addressed spatial light modulators (OASLM) or the blinding of the eye or the video camera.